In recent years, with a progress of digital technologies, electronic devices such as portable information devices and information home appliances have been developed to provide higher functionalities. With achievement of higher functionalities of the electronic devices, semiconductor elements incorporated into the electronic devices have been developed at a higher pace to provide further miniaturization and higher speeds of them. Among them, the application of a non-volatile memory having a great capacity, which is represented by a flash memory, has been expanding at a higher pace. Moreover, as a novel non-volatile memory in next generation, which has a potential of replacing the flash memory, a variable resistance non-volatile memory device including a variable resistance element (variable resistance non-volatile memory element whose resistance values change by application of voltage pulses: ReRAM element) has been studied and developed. As defined herein, the variable resistance element refers to as an element having a characteristic in which its resistance values reversibly change in response to electric signals and being capable of storing information corresponding to the resistance values in a non-volatile manner.
Patent Literature 1 discloses a variable resistance element including a variable resistance layer having a stacked-layer structure in which transition metal oxide layers which are different in oxygen content are stacked together. In this variable resistance element, a redox reaction can take place selectively in a region of the interface between a variable resistance layer with a higher oxygen content and an electrode by alternately applying voltages with different polarities. Thus, a resistance changing phenomenon can take place stably.
Patent Literature 2 discloses a resistance memory element which includes a lower electrode, a resistance memory layer 14 formed on the lower electrode, and an upper electrode formed on the resistance memory layer, stores a high-resistance state and a low-resistance state, and switches its resistance state between the high-resistance state and the low-resistance state by application of voltages, the lower electrode or the upper electrode having a first conductive layer provided at the resistance memory layer side and comprising precious metal, and a second conductive layer being in contact with the first conductive layer, being thicker than the first conductive layer, and comprising non-precious metal.